1. Field of the Invention
The present invention relates to a near field light probe having a resolution equal to or less than a wavelength of light, a near field optical microscope, a near field light lithography apparatus, and a near field light storage apparatus that have the near field light probe.
2. Related Background Art
Advances in micro-fabrication of microscopes, machining apparatuses, and storage apparatuses that use light will require resolutions of 100 nm or less in the future. Such microscopes are used in the fields of micro-fabrication-oriented biotechnology such as IVF-ET (In Vitro Fertilization and Embryo Transfer) and gene therapy. The photolithography apparatuses are used for manufacturing semiconductor memories that store a large amount of information such as information from the internet and high resolution video images available in an information society. The storage apparatus includes a large-capacity optical disk.
High resolution of the apparatus using light has been developed in the past by increasing NA of lens and employing light sources of shorter wavelengths. However, this approach places limitations on the development of apparatuses having still higher resolution. In order to overcome this technical limitation, use of near field light optics without using a lens is beginning to receive more attention. Near field light provides a resolution independent of the wavelength of light, and achieves high resolution that overcomes limitations due to diffraction. A near field optical microscope based on near field light has been developed. The development of a machining apparatus and a storage apparatus that employ the near field optical microscope is in progress.
The aforementioned near field optical microscope has an optical probe formed of a sharply pointed optical fiber that is enclosed with a light-blocking metal film having an aperture of about 100 nm formed in the tip of the light-blocking metal film. Light is coupled into the optical fiber from behind the aperture so that the near field light penetrates through the aperture out of the fiber to illuminate an object under test. The light reflected from or transmitted through the object is detected, thereby allowing observation of the surface condition of the object with a resolution as high as the size of the aperture (Japanese Patent Application Laid-Open No. 7-174542 and U.S. Pat. No. 5,677,978).
The resolution of the aforementioned probe is determined by the size of the aperture. In order to further increase resolution, the aperture is required to be made smaller. However, a smaller aperture, decreases the intensity of the near field light that has penetrated through the aperture. If the resolution of the near field optical microscopes is to be improved, the intensities of reflected light and transmitted light detected near field light after reflection or transmission decrease, and therefore the SN ratio of the detection signal deteriorates. Therefore a smaller aperture suffers from the problem that observation under a microscope is a time consuming work.
With a machining apparatus using the optical probe, if the aperture is made smaller in an attempt to perform micromachining, the amount of transmitted light decreases, machining time becomes longer, and throughput is decreased. With an optical storage apparatus using the optical probe, if the aperture is made smaller for implementing a larger memory capacity, time required for recording and reproducing data becomes longer.
An object of the present invention is to provide a near field light probe that can offer near field light of a sufficient intensity even if the aperture is made smaller in an attempt to improve resolution, and a near field optical microscope, a near field light lithography apparatus, and a near field light storage apparatus that have the aforementioned near field light probe.
In order to solve the aforementioned subjects, the present invention provides a near field optical microscope, a near field light lithography apparatus, and a near field light storage apparatus that employ a near field light probe. The near field light probe is characterized in that a light-blocking film has an aperture comprised of slits formed around a major opening, which means a portion of the aperture other than the slits, and light emitted from a light source is polarized in a predetermined direction and then introduced into the slits of the aperture from one side of the light-blocking film, thereby causing near field light to emanate from the aperture.
According to an aspect of the present invention, there is provided a near field light probe wherein a light-blocking film has an aperture comprised of a major opening and slits surrounding the major opening, and light emitted from a light source and polarized in a specific direction of oscillation of electric field vector comes into the aperture from one side of the light-blocking film, whereby a near field light usable for probing emanates from the major opening.
Each of the slits in the present invention may have a width substantially at most the same as a dimension of the major opening.
The longitudinal directions of the slits in the present invention may be either parallel to or at an acute angle with the specific direction of the oscillation of the electric field vector.
The aperture in the present invention may have a substantial cross shape, the crossing of which cross shape is the major opening, and the longitudinal directions of slits of the aperture in the present invention may make about 45-degree angles with the specific direction of the oscillation of the electric field vector, respectively. In this embodiment, the major opening may have a smaller dimension in the specific direction of the oscillation of the electric field vector than a dimension of the major opening in the direction making a right angle with the specific direction.
The aperture in the present invention may have a substantial H-shape the bar of which H-shape is the major opening, and the light polarized in the specific direction of the oscillation of the electric field vector is a light polarized in the longitudinal direction of the H-shape. In this embodiment, the slits that form the H-shape may be located so as to make the distance between two of the slits adjacent to each other increases with increasing a distance from the center of the H-shape.
The aperture in the present invention may be provided at a sharply pointed tip portion of an optical waveguide covered with the light-blocking film. In this embodiment, the sharply pointed tip portion of the optical waveguide covered with the light-blocking film may have a shape of a pyramid, and the slits may be substantially aligned with edges of the pyramid.
The light-blocking film in the present invention may be flat and the aperture may be formed in the light-blocking film. In this embodiment, a plurality of the apertures may be formed in the light-blocking film.
The probe in the present invention may be provided on an elastic body.
According to another aspect of the present invention, there is provided a near field optical microscope incorporating the near field light probe of the present invention.
According to a further aspect of the present invention, there is provided a near field light lithography apparatus incorporating the near field light probe of the present invention.
According to a further aspect of the present invention, there is provided a near field light storage apparatus incorporating the near field light probe of the present invention.